counter is just an identifier for the variable, you can choose the name -identifier-
that you want for example i,j,k or counter my advice is that you pick up some good C++ book and learn the basics again, like VARIABLES give me your e-mail and i'll send you a link to download a good book.

There is no need for that in your code because they are overwritten a moment later. But it is a good idea to initialize your variables:
* If your code ever changes you won't bump into undefined behavour because you used it without initialization.
* Excessive assigment will be optimized away anyway.

Okay, I tried to separate the numbers with a "," but after the last number the "," remains here. I tried at random(without actually knowing it lol) to use an if statement but it doesn't seem to work lol.

Check my code above or vlad from moscow one.
EDIT: vlad from moscow one does output upper bound :(
And it syntaxically wrong.
I realized, that you might doesn't know how to use ternary operator, so I replaced it with if:

Great explanation MiiNiPaa. Thanks :)
I tried it and it worked perfect. You just missed ++n1 after std::cout<<", "; but it's just fine :D Thanks buddy :)

More question:
Why std::cout and not using namespace std;

How does using namespace std; affect the whole program in case it's more complex? This is a simple program, so obviously it's not a big deal, but what happens in case of bigger, more complex programs, where different namespaces are used? Would it be as follows:
using namespace std;
using namespace x;
using namespace y;
using namespace z;
...etc
?